The aim of this project is to study the regulation of the synthesis of mouse immunoglobulin (Ig) protein by combining biochemical and genetic analyses. Cloned cDNA sequences for 315 heavy chain will be used to study the gene structure for alpha chain in myeloma cells. Results will be compared with those obtained with germ line cells to determine the gene number in each case and to decide whether a gene rearrangement occurs in the selection of a H chain species for production. The synthesis and processing of L and H chain mRNA will also be examined. The studies will involve the comparison of mouse myeloma MOPC 315 wild type and variant lines defective in Ig production. Variant lines will be isolated and classified into 3 groups: (a) those that synthesize Ig but do not secrete it; (b) those that synthesize Ig proteins with altered structure; (c) those that synthesize Ig proteins at altered rates. These will be examined biochemically for possible defects in Ig-specific gene structure, RNA synthesis, processing, transport, and translation of polypeptide products, as well as for maturation and secretion of Ig protein. Methodology will include such techniques as growth in tissue culture, agarose and acrylamide gel electrophoresis of DNA, RNA and protein, sucrose and CsCl gradients, in vitro translation, immune precipitation, cloning of DNA sequences, hybridization of RNA or DNA to labeled DNA probes. The results of these studies will give information about gene structure and the regulation of synthesis and secretion of a specific protein by mammalian cells. In addition, they may advance our understanding of antibody synthesis and the origin of antibody diversity as well as the processes involved in the neoplastic transformation of a normal lymphocyte.